1. Filed of the Invention:
The present invention relates to a cephem derivative having a specific crystal structure and a process for the preparation thereof.
2. Description of the Related Art:
7.beta.-[(Z)-2-(5-Amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetamido]-3-( 4-carbamoyl-1-quinuclidinio)methyl-3-cephem-4-carboxylate and its possession of excellent antimicrobial activity are described in Japanese Patent Laid-Open No. 123,189/1987. That described in the same disclosure is however an amorphous substance or type I crystals. The compound of the amorphous form is obtained by a method such as freeze drying of its corresponding solution, rapid distilling-off of its solvent, rapid deposition of the compound by addition of a poor solvent, or the like. On the other hand, the type I crystals are obtained by crystallizing out from an ethanol-water mixed solvent. Of those, the type I crystals is very poor in stability in that the residual rate of the compound when stored (in a hermetically sealed container) at room temperature for 1 month is 50% or lower. Although the amorphous compound is better in stability than the type I crystals, its residual rate when stored (in a hermetically sealed container) at room temperature for 6 months is 90% or lower. Therefore, it cannot be said that the amorphous compound has sufficient stability.